1. Field of the Invention
This invention relates to the removal of deposits comprising heavy hydrocarbonaceous materials and finely divided inorganic drilling fluid solids from a wellbore using an alkyl polyglycoside surfactant composition.
2. Background of the Invention
Many oil wells are drilled using oil-based drilling fluids. These drilling fluids may contain emulsified oil, mineral oil, synthetic oil, diesel oil, residual crude oil or other suitable organic liquids having a suitable density and other properties required in a drilling fluid. These drilling fluids typically contain weighting materials, which comprise finely divided solids, and also, immediately upon initiation of drilling, finely divided inorganic solids removed from the subterranean area through which the well is drilled. These solids become oil-covered during drilling and may be covered with not only the oil used in the oil-based drilling fluid, but also with some crude oil when an oil-bearing formation is penetrated. During drilling operations, some fluid from the drilling fluid leaks off into the formation, as well known to those skilled in the art. As a result, some of the solids in the drilling fluid are deposited on the formation face or in the near wellbore formation. Such deposits on the formation face are commonly referred to as "filter cake". The solids comprise finely divided inorganic solids coated with emulsified oil or heavy oil components. These solids tend to agglomerate and are difficult to displace from the formation, even when the production of fluids from the formation is commenced. This can result in formation damage and result in the production of lower volumes of fluid from the formation than would otherwise be possible. These drilling fluid solids, when coated with emulsified oil, tend to agglomerate and form masses of solids which are not readily dislodged from formation pores, passageways and the like. Further, cakes of the solids deposited on the face of the formation may not be removed by the production of fluids from the formation. In both instances, the production of fluids from the formation is restricted.
Since it is desirable to produce the maximum volume possible from the formation, methods have long been sought for remediating such formation damage and for removing such drilling fluid solids from the face of the formation and from the near wellbore formation.